#include <stdio.h>

#define swap(t,x,y) t k;k=x;x=y;y=k 

int main()
{
    int x = 10, y = 20;
    printf("x=%d,y=%d\n",x,y);
    swap(int, x, y);   
    printf("after swap: x=%d,y=%d\n",x,y);
    return 0;
}